A large variety of materials have been proposed and in fact used and offered commercially as golf club heads and faces. These materials have been applied monolithically or as inserts in the club face in an attempt to achieve more distance and/or more control over the ball. The list of materials includes polymers, ceramics, and metals, typically the most common stainless steels, BeCu, and lately various titanium alloys, and shape memory materials such as NiTi based and copper based alloys.
Each of these materials has individual properties, different from each other but basically uniform unto themselves and hence provide a surface on a golf club that impacts the golf ball with essentially uniform mechanical properties across the face. For example, a typical titanium alloy such as Titanium 6-4 has a modulus of about 15 million psi and a yield strength of about 120,000 psi at a strain of less than 1%. Other materials will have different moduli and different yield strengths with different associated strain levels but as noted uniform properties as to themselves as used on the face of a golf club.
Since the mechanical characteristics (club speed, materials properties, geometry) at the impact of the club face with the ball determine the course (trajectory, distance, dispersion) of the ball; control of the materials properties can be key to control of the course of the ball. Club head speed and geometry being constant or independent of the specific properties of the material used as the impact surface of the club.